Mud Engineering

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 

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

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

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

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 

  

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 

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

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X- Link

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Barite Plug

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Marble Pill

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Gunk Squeeze

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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   

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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     

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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 

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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       

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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 

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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 

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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 

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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 

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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 

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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 

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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.

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A grease pill is the most effective solution.

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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 

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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 

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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 

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1. 2.

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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 

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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 

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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 

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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 

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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 

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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 

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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

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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  

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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. 

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

Carbon Dioxide 

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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 

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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 

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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 

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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 

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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 

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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 

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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 

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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 

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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.

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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 

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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 

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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 

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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.