Drilling Formulars 2

PRESSURES and PRESSURE GRADIENTS 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

Pef = Pov – Pp Pov =(ρb H) / 10 Ph = (ρW H) /10 =1.03kgf/cm2 ρb = φ · ρfl + (1 – φ) · ρmax =2.31g/cm3 Gov = (Pov · 10) / H Kgf/cm2/10m Gp = (Pp · 10) / H Pfr = Pp + K (Pov – Pp) K = v /(1 - v) , default K = 0.67. Gfr = (Pfr · 10) / H Gfr = Gp + ( 2ν ) (Gov – Gp) elastic 1-ν Gfr = Gp + ( 2ν ) (Gov – Gp) – water Gfr = Gov – plastic

1.

2.

3.

Δt = Δtmax (1 – φ) + Δtfl · φ φ =1.228 [ (Δt - Δtmax)/( Δt + 200)]

3.

∆ tin−∆ tmax ∆ tin+∆ tmax Pb=Pmat−2.11 ¿ ]

4.

5. 6.

∆ t−∆ tmin ∆ t−∆ tmax Pb=Pmat−2.11 ¿ ] Pmax = 2.75g/cm3 , Δt fluid =200 µsec/ft

Equivalent Depth Method (Peff constant ) 1. 2. 3.

EMW=

4. 5.

X 10 ( PTVD )+ MW

B. Forcce = Wair x (Dmud/Dsteel) 10. Tbend = 15.52x α xD x Af D(in), Af (cm2) , α (o/30m) 11. Tben (psi) = 218x α x ODcsg 12. Wet Weight = dry weight x B.F 13. W(TJ) = 0.15 x Wd.p

surface

14.

∆ Pce=E ρ0.8 Q1.8 μp 0.2

1.

Dn = dc [1 –(Dmud/7.85)]

( Gfrac , sh−Dmud , H ) x Hsh ∆ Pch= 10 RHEOLOGY τ =μ γ (MAASP) 1.

R 60 N 12W D∗106 ¿∈[¿ ] D−exp ¿

)

2.

……

3.

∆ Pds= V=

ff L ρV 2 R

∆ Pdb=

( Gfrac−Dpor ) x H 10

6.

3.

( )

CASING 1.

Q A

Vnozzel = Q/∑An , n =3 Rolla

∆ Pfric=

4 3 n+ 1 ff (lam )= n ℜ

(

τ =τ 0 +k μ γ

5.

n

)

600

∆ Pturb=

3.

∆ Ptur 5.

600

∆ Pbit=

ρV 2 +0.1 2

∆ Pbit=

ρV +wWOB 2

3

2.

T Tmax= D.F

1. 2. 3. b. 1. 2. 3. 4.

Qt = 0.0515nL(D2 –d2/2) Qt = 0.0386nLD2 Nr = Qr/Qt PUMP HORSEPOWER(HP) HP = W X w W = SPP/Density w = Density x Q HP = Q x SPP

∆ Pann=

2

c.

FRICTION/ PRESSURE LOSS

6.

2

…. .w =.25 7.

Power , bit=Q x ∆ Pbit 8.

ff L ρ V 2 R 2−R 1

(

Kρ V 2 2

∆ Ptot=∆ Pfric +¿

300

300

ρV 2 1 [ −1] 2 Cv 2

4.

24 ff (lam )= ℜ

Q σmud ( E+ H )−σnor (H ) 3. V= 11. Hi= 5. A Ttotal=Tweight +Tbend +Tcement plug ( σnor −σmud ) +0.67 (σsed−σnor) SPP X Qr 1. Ppump ( HP ) = n n n 4. 400 x ∩m x12. ∩t Gsed−Gp ∆ tnct n E =Rob Dc obs C nor air gap, H = water height, =( ) =( ) =( ) =( ). Force=Wair −apparent W A=π ( R 22−R 12 ) B Gsed−Gnor ∆ tcal Rnor Dc nor C obs 1.03 kgf 6. σnor= /10 m 5. Tension = weight – buoyancy cm2 n = 3 (seismic/sonic) SPP X Qr13. 6. Apparent weight = Wair – B. n =1.2 (Resistivity / Dc-Exp) Ppump ( kw )= Force Gnor = 1.03Kg/cm /10m 600 x ∩m x ∩tff (lam )= 8 2 n+1 7. Apparent Weight = Wair x B.F 8. B.F = 1- (Dmud/Dsteel) n ℜ D –EXPONENT EATON’S METHOD (Less Precise to EDM)

1. 2.

4. R ρVD −4 μ p (cp )=θ −θ ℜ= 4. 10 ∗Hshoe∗Gfr∗C 6. 3 a 60 N μ Vi , H ( m ) = ∗[ Hshoe ( Gfr−Dmud ) + HDmud−10∗Pp ] ∗Gnor Pp ( Dmud−Dinflux) τ 12W 0( cp )= 2 θ −θ 5. ff ( turb )= y R−z 6 7. 5. Ca = annular capacity below D∗10 shoe (Dm /m) 6. Dc−exp=¿ 6. Expected Hole Problems log n+3.93 G 7. Functions of casings(2,3,5,3) (¿ θ600 /θ 300 ) y= 8. log 50 TENSION CALCULATIONS FOR 7. Dc- exp and D-exp increases log2 CASINGS vs depth (for NCT) n=¿ 8. Dc- exp and D-exp decreases 1.17−logn z= vs depth (for OPF) 9. 1. 7 9. Pipe resistance HYDRAULICS Po ( Dc−exp ) nor ¿ = ANNULUS D . F=¿ load Pn ( Dc−exp ) obs a. PUMPS load inside wall 10.

Peff(h1) =Pov(h1)-Pp(h1) Pp(h2) = Pov(h2) –Pef(h1) Pov = Gov*H , Pp = Gp*H

BIT PRESSURE LOSS

4.

….k =

Apparent viscosity K = flow consistency index n = flow behavior index n <1 = psedoplastic, n=1 = Newtonian n>1 = Dialactant

3.

[ ( )]

2.

=

()

plastic viscosity

(Gmud , max−Dpor , H ) x H n τ =k μ γ ∆ Pd= 2. 10

Dc – exp = d-exp/ MW Dc –exp = D-ex * (MWnor/MW)

μ

z 2 ff ( turb )= y [ R] 3

drill string

NEUTRAL POINT 1.

n =1 if plastic condition

1.

5 CASING SETTING DEPTH CON

R = KNe(W/D)d

(

9.

2.

( )

OVERPRESSURE MEASUREMEN T 1. 2.

W D ¿ ¿ R =¿ N

Power , bit ∝ Qmud 3 9.

Power , bit ∝ OD−4 10.

Velocity ∝OD−2

11.

Pshoe=gρmH + ∆ Pstart

)

12.

10.

6.

∆ Pstart=

∆P H ∆H

Vav=

centistokes x specific gravity = centipoise

Vi+Vf Vf Cv √ 211.gh = = 2 2 2 Lmin ,dc =K

COMMUNICATING VESSELS

13.

( )

√

14.

Velocity, min = 10-1 m/s

15.

ROC=

4 SPP=∆ Pce+ ∆ Pds+ ∆ Pbit+ ∆OD Pann −ID 4 ¿ 16. 1. π¿ Ph ∆ Pann Mp=¿ ECD= + > gρm h h 4 4 OD −ID KICK ¿ 1. 2. π gρmH =Pann+ gρmh+ gρk ( H−h) ¿ Md=¿ 2.

3. 4.

Pann ρk=ρm− g ( H −h )

Mp = 2 x Md t = (OD –ID)/2

Mtwist ( max ) = STOKES LAW

τ x Mp OD 2

1. 6.

gρsteel

3

r τ x Md + 6 μπrVlimit ( 4 π3r )=gρmud ( 4 πMbend 3 ) ( max )= OD 2

2.

2

r ( ρsteel− ρmud) μp 2 Vlimit= g ¿ 9 3. 4. 5.

7.

) 8.

V =C v √2 gh = o.65 (homog)

Hexagonal Kelly, circular inn

6 π A= √3 R2− ID2 4 4

Pulling Action = Pdp + Pdc + P (Kelly+bit) +g

π ρmHdp x 4

Time = Distance/(Vinitial +Vlimit) Time = Distance/ Vaverage …. C 9.

OD2dp) Unitary Volume of Pipe

V u=

π 2 ID 4

5.

Torque=L2 M 1 T −2

360 2 πxdog−leg

6.

2

1

Power=L M T

−1

7.

5.

3

Pressure x Volume

Torque * RMP = Power

15.

GENERAL EQUATIONS

−2

( )

nozzle

14.

1

−1

Pressure=L M T WOB(ibf ) 4. ibf 2 1 −2 Wdc x BFxcosθ Energy=L M T ft

psi 1. ) Cv H ∆ P psi ft Vav= 2 g ( hh ) [1− K] = 1.2 = Specific HP = (HP/A ) 2 hh 12. ∆ H ft 300 ( d 2−d 1 ) 13. Specific WOB = WOB/ODbit τgel (

3.

(OD2dc –

Length units 1mm =0.1cm=0.001m =0.000001km =0.03937in =0.003281ft =0.001094yd=6.21e07 mi Area Units 1mm2 = 0.01 cm2 = 0.000001m2 = 0.00155in2 = 0.000011ft2 = 0.000001yd2 Volume Units 1cm3 =0.000001m3 = 0.001 ltr = 0.061024 in3 = 0.000035ft3 = 0.000264 US gal = 0.000006brl Mass Units 1g = 0.001kg = 0.000001tonne =0.002205lb =0.035273oz Density Units 1g/ml = 1000 kg/m3 = 62.42197lb/ft3 = 0.036127 lb/in3 Volumetric Liquid Flow Units 1L/sec =60 L/min = 3.6 M3/hr = 2.119093 ft3/min = 127.1197ft3/hr =15.85037gal/min = 543.4783bl/d Volumetric Gas Flow Units 1m3/hr = 35.31073scf/h =0.588582scf/m Mass Flow Units 1kg/h= 2.204586lb/hour = 0.000278 kg/s =0.001t/h Pressure Units 1bar = 14.50326psi = 100kPa = 0.1MPa = 1.01968kgf/cm2 = 750.0188 mm Hg = 0.987167atm Dynamic Viscosity Units 1cp = 0.01poise = 0.000672 lb/ (ft·s) Kinematic Viscosity Units 1Centistroke =0.01 Stroke = 0.000011ft2/s = 0.000001m2/s Power 1 HP = 550 ftIbf/s = 0.7457 kilowatt = 1.014 PS or CV Dimensional Analysis 1.

1

1

Force=L M T

Diferential Discharge, Diferential Gas flow, Rock Dilactancy, Thermal efects, Osmosis, Reservoir Depletion Importance of Pp, Pov, Frac Knowledge

Functions of Drilling Fluid = 10 reasons! CONDUCTOR PIPE To protect the shallower formations from any contamination due to the drilling fluids; to prevent dangerous wash-outs and erosion of the loose, unconsolidated topsoil, which can, sometimes, result in big problems for the stability of the rig itself SURFACE CASING   

Dynamic Viscostity=L−1 M 1 T −1

1. Casing Program design (5) 2. Cementing Design (1) 3. Drilling/Mud/Hydrulics (5) 14. −2Well Control design (1) 5. Well Cost (1)

8.

F 0 Linear Weight ( )=L M T L Specific Power (



 

Mud Additives –weighting agents, Viscosifiers, Filtration control Agents, Deflocculants, shale stabilization agents, lost circulation  1 −3Defoamers.  agents,

9.

P )=L0 M T A Mechanism of Bit drilling :

scrapping/gouging, Plouging &grinding, Chipping & crushing, shearing, Erosion

10.

P −2 PressureGradient ( )=LBit M 1 T −2 – Bouncing Mis-working h (WOB), slip &stick (bit choice),

  

Whiskhing (BHA arr) 11.

Tensile Load causes- String

bending, cement plug, P −2 weight, 1 −2 Specific Weight ( )=L shock M Tloading, high internal pressure h 12.

Surface Tension( 13.

0

1

14.

−1

Force/V = Pressure Gradient = Specific Weight =

L−2 M 1 T −2 OTHERS

−2 1. 2.

Advantages of OBM 1. maximum level of shale hydration inhibition 0 2.1 −1 consistent fluid properties 3. More competent cuttings 4. used for more than one well 5. bottom hole temperatures up to 300°C 6. flexibility, reduced corrosion 7. improved rig conditions Disadvantages of OBM High make-up cost, Environmental restrictions, Extra fire prevention precautions, Oil Compressibility, less efective Hole cleaning and cuttings suspension, more difficult kick danger evaluation

F )=L M T L

Specific WOB =

L M T

Normalized =(Vav/Length) = T-1

2. (ft3/ft)

=

THEORY Overpressures 1. Stress related Mechanism (tectonics, compaction disequilibrium) 2. Volume Increase Mechanism (Temperature rise, Diagenesis, Decomposition, H/C generation, Cracking, Bitumen) 3. Fluid Movement and Buoyancy (Osmosis, H/C Buoyancy, Artesian Pressure) 4. OP fluid redistribution (transference) Under Pressures

OD/t > 20 = thin wall (CP) OD/t < 20 = thick wall (DP)

Advantages of GBM – Avoid loss circulation, Improve ROP, larger bit life, reduced water loss to formation



To protect the potential fresh-water levels from the contamination of the drilling fluids; to allow the installation of the bop stack; To help supporting the weight of the successive drilling strings and the production equipment INTERMEDIATE CASING To seal of troublesome formations, such as weak zones with low fracture gradients, overpressured intervals, salt beds, sloughing shales, reactive formations, deviated sections, etc.; to get closer to the target; to allow the use of higher density muds, being placed in higher fracture gradient formations (minimum choke margin required: 40 kgf/cm2); to install higher performance bop stack; To isolate intermediate mineralized formations PRODUCTION CASING OR PRODUCTION LINER The isolation and protection of all the zones above and within the production levels; Housing for all the production equipment; The execution in safe conditions of all those operations which are usually required during the production life of a well; The containment of the producing fluids in case of production string (tubings) failure. THE MAIN ADVANTAGES OF A LINER ARE:  Costs containment;  Decrease of the weight of the tubulars to handle (efects on rig selection);  Better hydraulics;  Mechanical integrity when production starts;  More flexibility in completion schemes. THE MAIN DISADVANTAGES OF LINER INSTALLATION ARE:  Risk of poor pressure integrity in correspondence of the liner top because of poor cementation or due to wear of the casing on which the liner is hanged;  Risk to cement the liner running equipment;  Difficulty in obtaining good cementing jobs due to the small clearance between casing and liner or hole and liner;  Need to install a bridge plug above the liner top in case of bop removal in case the completion string has not been run and landed yet..

Importance of Gradients Analysis While Drilling. The starting point of a correct and reliable well planning and design is represented by the prediction and the evaluation of the pressures the well will have to face during the drilling activity; therefore, all eforts have to be made to determine: -Overburden pressures and pressure gradients - Pore pressures and pressure gradients - Fracture pressures and pressure gradients. Correct pressure gradients evaluation while drilling will lead to proper selection of the well parameters: - Casing setting points and casing design - Mud and cementing programs Hydraulic program - Bit selection - Drill string design and stabilization - Rig selection - BOPs & wellhead selection Equipment selection - Hole problem individuation Why Most Techniques for Overpressure Analysis Use Shales as Reference? 1. Normally pressured rocks and abnormally pressured rocks only coexist if separated by “permeability barriers” or “seals”, which act also as “pressure barriers”. These barriers or seals can be created by any material or combination of materials which reduce or impede the movement and passage of fluids within the subsoil and can be of physical, chemical origin or a combination of both. 2. Clays and Shales constitute the most common permeability barrier generally considered responsible for overpressure occurrences and most techniques for abnormal pressure detection are applied in these two categories of rocks. Pore Pressure Gradients calculations from Seismic Data Analysis (1) Pov = Pef + Pp (2) If at the considered depth H 1, the rock has normal compaction and also normal pore pressure, assuming a value equal to the hydrostatic. (3) If the rock at the depth H 2 was impeded, for any reason, then will have pore pressure above hydrostatic. (4) If the two rocks are made both by the same lithology and have the same transit time, then they have been subjected to the same compaction pressure. (5)Therefore, once calculated the overburden pressure at the depth H1 and knowing that the pore pressure gradient is normal (equal, for instance to 1.03 kg/cm 2/10 m), by applying the above mentioned equation the efective compaction pressure can be calculated: Pef,H1 = Pov,H1 – Pp,H1 (at depth H1) (6) Moving to the depth H 2, the overburden pressure is easily calculated, being the overburden gradient already available; Pp,H2 = Pov,H2 – Pef,H1=H2 (at depth H2) (7) The Pore Pressure Gradient at H2: GP = (PP x 10)/H2 Kick Tolerance: The volume of maximum influx (kick) that, once entered into the wellbore, can be circulated out with a “constant bottom hole pressure” method without fracturing the formation below the shoe of the previous casing. Yield Strength of Steel: In steels, yielding phenome-non occurs after the elastic limit. For materials used to produce tubular goods, API specifies the yield strength as the tensile stress required to produce a total elongation of 0.50-0.65% (depending on steel grade) between the gauge length. Casing String equipped with External Attachments (Centralizers, Scratchers)? Casing string should be equipped with centralizers & scratchers to assure acceptable casing centralization and to enhance mud removal operations. These equipments are attached in the outer sections of the casing.

Functions of Drilling Fluid: - Facing formation pressures and supporting well control aims (Density); - Hole cleaning with removal of cuttings from the bottom of the well providing their transportation up to surface (Density & Viscosity); Cuttings and solids suspension when mud circulation is temporarily stopped (Gel Strength); - Protection and stabilization of bare borehole walls (Mud Cake); - Cooling and lubrication of bit and drill string (Lubricant); - Reduction of drill string and casing weight, fatigue and wear (Density), - Corrosion Control (pH); - Data acquisition about rocks and formation fluids. - Circulate the kick out of the well. Define: the following (also Adv. and Disadv.) Cake Thickness: the cake can stop filtration and stabilize wellbore walls. Filtrate: the liquid lost by a drilling fluid into permeable formations can cause formation damage and hole instability, though a certain amount (the “spurt loss”) can enhance penetration rate; Yield Point or Yield Value: this quantity represents the initial resistance ofered by a fluid to be put in motion, that is the stress required to make a fluid to pass from static to dynamic conditions; Plastic Viscosity the internal resistance to fluid flow of a Bingham plastic, expressed as tangential shear stress in excess of the yield stress divided by the resulting rate of shear. Spud muds are used to drill surface holes. Usually the main function of a spud mud is to clean the well from the cuttings. Surface hole Jumbo bits have bigger teeth than normal bits, generating bigger cuttings. Because surface holes are of such large diameter (up to 36"), annular velocities are low, even at maximum pump rates. This means that spud mud viscosities have to be usually high. Why Multistage Mud Substitutions are necessary? 1. When Δ is very large (To avoid shocking the formation with high ΔP). 2. In case of very deep well is being drilled. Main Advantages of OBM over WBM and Their Main Disadvantages? Advantages: - A properly conditioned oil mud should have no efect on a shale formation. Therefore, gauge hole can be drilled through water-sensitive shales -The non-polar environment results in consistent fluid properties, low chemical maintenance costs, stability under high temperature conditions, minimal efects on properties from drilled solids, good resistance to salt and gypsum contamination and good protection of drill string against the corrosive gases H 2S and CO2. -Formulation for low fluid loss results in low torque, especially in deviated holes, minimized diferential sticking problems and low formation damage factors in oil Res. -Formulation for high fluid loss results in high rates of penetration. The low solids content and reduction in cuttings stickiness also improves penetration rates. -Oil mud can be used for more than one well due to their stability. -Low aromatic oil-based fluids result in improved rig conditions, low odour, clean handling on the rig, minimal efects on the marine environment, improved rheological properties and high flash point giving extra safety. Disadvantages: - High make-up cost. Environmental restrictions including cuttings & chemical waste disposal. Extra fire prevention precautions are necessary. - Reduced rates of penetration in some areas. - Gas intrusion often results in barite settling.

- Compressibility of the base oil makes volume and density estimations difficult. Hole cleaning and cuttings suspension may be less efective. - Rubber materials (such as hoses or BOP) may dissolve too rapidly in oil-based fluids. - Some types of electric logs are inefective in oil-based fluids. - Gas intrusions are more difficult to detect using oil-based fluids. In Bit Design, what’s meant by Bit Offset, Journal Angle and Back-Rake Angle? Bit Offset is the horizontal distance of the cone axis from the center of the wellbore” or as “the angle of which is necessary to rotate the cone axis to make it pass through the center of the wellbore”. Journal Angle is the angle formed by a line perpendicular to the axis (or centerline) of the journal and the axis (or centerline) of the bit. Back-Rake Angle is the angle at which a PDC cutter attacks a formation. High back rake angles (20-30o) improve impact and wear resistance. Low back rake angles (515o) increase ROP. (The back rake angle exists only for fived cutter bits). Roller Cone and Fixed Cutter Bits IADC Classification. A. Roller Cone Bit: Roller cone are classified by IDAC through four-character design or application code. First three Characters are numeric and fourth Character is alphabetic. - Numeric Characters define: 1. First Character: Series “General Formation Characteristics are compressive strength and abrasivity”. 2. Second Character: Type “General formation characteristic is degree of hardness”. 3. Third Character: Bearing & Gage “General purpose is to design bearing and protect gage”. - Alphabetic Character defines: 4. Features Available (4th) “Most Significant Feature or Application Listed – Optional” B. Fixed Cutter Bit: (Drag Bits – N. Diamond Bits - Synthetic Diamond Bits PDC TSP): IADC introduced a classification system consisting of four character codes for fixed cutter bit including natural diamond and PDC cutter bit. • Code 1 - Cutter Type and Body Material (D, M, T, S, O) • Code 2 - Bit Profile (1-9) • Code 3 - Hydraulic Design (1-9) • Code 4 - Cutter Size and Density (1-9). Cutting Mechanism of PDC Bits? The cutting mechanism of PDC bit is shear mechanism. PDC cutters cut the formation in shear. The shearing action is the most efficient cutting action when operating under identical conditions. Due to this mechanics the required drilling energy is less compare to cracking and grinding mechanism. Main Functions of Spacers and Chemical Washes in Cementing Operations? Due to the high incompatibility existing between most drilling muds and cement slurries, to prevent mixing between these two categories of fluids with adverse efects on thickening times, rheology and mud displacement efficiency, chemical washes (water with dispersants) or spacers (water added with polymers and weighted) or both must be pumped ahead of the slurry to keep it separate from the drilling mud. Troubles and Dangers of Drilling Through Shallow Gas Formation: Shallow gas represents an overpressure zones which causes diferent problems in drilling process. Shallow gas encountered can causes kick or even blowout because gas reduces mud density while mixing with mud and thus pore pressure becomes more than mud pressure. Possible Causes of a KICK during Drilling Operation: - Surge (Downward Flow) efect due to “Trip” velocity

-Moving the drilling strings too quickly during swabbing (Upward flow) - Incorrect bottom hole assembly (BHA) sizing. - Too heavy mud and cement slurry (this leads to first fracture, then kick) -Too light mud (this leads to kick, no fracture). - Retrieving to surface geophysical instr. too quickly through casing Possible Problems Faced by Drillers: - Pipe sticking. - Having reservoir fluids inside the borehole (kick). - Mud Circulation loss. - Fracturing the bare rock (this may be due to quick surge or may be due to incorrect choice of outside diameter of bottom hole assembly or too heavy mud) Types of Controlling During Circulating Process: - Primary control: only drilling mud. – Sec.: mud and BOPs. – Tert.: BOPs & other fluids like barite pillows. Thin Wall Tubular Elements in Oil Industry: It’s the conductor pipe with OD/t ˃ 20 3 Phenomena of Bit Miss-Function: -Bit Bouncing due to incorrect weight on bit (WOB) -Stick and Slip due to inappropriate bit choice VS formation - Whirling due to mismatching of BHA configuration VS WOB; stress level increases. Why Mud Circulation Continuation into the Well Isn’t Preferable While Fishing: - Pumping mud will put solids to the tool required to be fished. - It will add more compaction to the tool due to solids contained in the mud and the BHP. Why we should avoid Mud Turbulent Flow Inside Uncased Annular Spaces. - To avoid hole erosion - To prevent removal of filter cake - To avoid rock fracture limit - To avoid large annular pressure losses - To avoid drill cutting attrition through the tumbling efect in annulus - Makes downhole instrumentation measurements unreliable. Disadvantage connected to TOP DRIVE, and to BICENTER BIT Adoption. Bi-Center Bit: 1. Damage to the casing 2. Impossible to fully stabilize because the largest stabilizer size that can be used is the pass through diameter. No stabilizer can be placed immediately above the bit because of geometry 3. While being run into the well: going down inclined and provide damage to the bit itself among friction. TOP Drive: 1. Hook load capacity reduction 2. More wear on drilling line Fundamental Consequences Resulting from Pressure Shocks at Bottom Hole Level (Uncased HC Bearing Formation): - Kick possibility. Formation Fracturing. - Mud Loss. Diferential sticking of the Drill string. Cement Fracturing over Shoe Level. Fundamental Rheological Parameter that is a Function of Yield Value and Plastic Viscosity: Bingham number, Bi Fundamental Rheological Parameter that is not a Function of Yield Value and Plastic Viscosity: Reynolds number, Re Casing Functions: Allow the installation of the Wellhead and Bops. Allow to circulate the drilling fluid up to the surface. Isolate formations with diferent pore pressure and fracture gradients. Exclude formations which can cause drilling problems because of their geological characteristics. Protect productive formations. Advantages of Liner: costs containment, decrease of the weight of the tubular to handle (efects on rig selection), better hydraulics, mechanical integrity when production starts, more

flexibility in completion schemes. Disadvantages of liners installation: risk of poor pressure integrity in correspondence of the liner top because of poor cementation or due to wear of the casing on which the liner is hanged. Risk to cement the liner running equipment, Difficulty in obtaining good cementing jobs due to the small clearance between casing and liner or hole and liner. Bits Selection: based on, Method of drilling (rotary, turbine, downhole motor, air), Formation type and properties, Mud system, Rig cost, Bit cost. Factors Affecting Bit Trajectory: Gauge and placement of stabilizers, Diameter and length of drill collars, Weight on bit, Rotary speed, Bit type, Formation anisotropy and dip angle of the bedding planes, Formation hardness, Flow rate, Rate of penetration. Mechanisms responsible for Abnormal Pressure Occurrences: Stress-Related Mechanisms: E.g. is Compaction disequilibrium (vertical loading stress) or tectonics (lateral compressive stress); Fluid Volume Increase Mechanisms: E.g. is Temperature increase, water release due to mineralogical transformations of rocks (digenesis), hydrocarbon generation, bitumen and oil cracking to gas; Fluid Movements and Buoyancy Mechanisms: E.g. is osmosis, hydraulic or artesian pressure. Main Features of Lean Casing: It is based on drastic reduction of the clearances between hole sizes and casing sizes. Require less quantity of cement. Get less quantity of cuttings. Less quantity of mud is required. Less quantity of steel Disadvantages of Lean Profile: high risk while running Casing due to low clearances between hole sizes and casing sizes (from 1 to 1.5”). Swap: occur when BHA is run upward very quickly and a kick is developed at the bottom and the rock fractures downhole. Piston Effect: When the BHA is run up and down the well too quick. Advantages and Disadvantages when Bi-Center Bits Are Employed: Advantages: - It can drill larger hole than the internal diameter of the previous casing string; - Due to the geometry of it, the bit is free to move to one side of the hole during the trip through the casing. As a result, the bit is able to pass through a hole that is smaller than it drills. - Larger diameter hole is drilled in one operation. Disadvantages - Problems of drilling a smaller than expected hole, - Excessive cutter wear and poor directional characteristics. - Bits are not well adapted to maintenance activities like replacing, repairing, etc. - Impossible to stabilize fully. Tool Joints Effect - Additional increase in DP weight by 10% - Necessary to connect DP singles because the pipe wall thickness has to be reinforced. –Useful in anchoring the drill string at the rotary table. The Maximum Differential Pressure Value Equals the Drilling Balance Value @ Bottom Hole, or generally put, at the bottom level of the considered interval / drill interval. Which Degree of Hardness 5 Refers to One Place in Any Position of IEDC Roller Cone Bit? Doesn’t Exist Bumper it’s a type of jar able to provide shocks upwards and downwards. Most Common Causes of Formation Fracturing: - Surge; - Too heavy mud weight; - BHA disconnection.

Under Balance Drilling - Drilling time reduced; - more probability for kick occurrence. Types of Completion: (1) Open Hole Completions when the formation is self-supporting or when it is severely fractured to guarantee successful cementation. (2) Uncemented Liner Completions used to overcome production problems associated with open hole completions. - Slotted Liner; used where there is a risk of wellbore instability which could cause the formation to collapse and plug of all production. - Wire Wrapped Screens; used as a filter to strain out sand produced from formation. External Gravel Packs; used where sand is too fine or abrasive for a plain screen. (3) Perforated Liner/Casing Completions. (a)Single zone: Standard perforated; Fracture stimulation; Cased hole gravel packs. (b) Multi-zone: Commingled production; - Sequential zonal production; - Single string multizone segregated production; - Multi-string (dual) multi-zone segregated production Compaction Disequilibrium Mechanism causes the Occurrence of Abnormally Pressured Zones. The mechanism of “compaction disequilibrium” is related to the “rate of sedimentation”. During sedimentation, the materials that accumulate are subjected to continuously increased compaction, due to the weight of the overlying sediments. This gradual compaction initially causes a hydraulic imbalance due to the presence of fluid within the pores of the rocks; these entrapped fluids are slowly expelled from the pores until pressure equilibrium is reached again. In case of rapid burial, increasing overburden stress has to take place. But where the fluids cannot be expelled fast enough, the pressure inside the pores of the rock increases; this phenomenon is referred to as compaction disequilibrium and it implies that a certain part of the sediment weight is transmitted to the fluid inside the pores of the rock. Diagenesis of the Rock: Diagenesis is any chemical, physical or biological change undergone by sediment after its initial deposition and during and after its lithification, exclusive of surface alteration (weathering) and metamorphism. Osmosis is defined as “the spontaneous flow of a solvent (usually water) through a semi-permeable membrane separating two solutions of diferent solute concentration (or between a pure solvent and a solution) until the concentration of each solution (that is their chemical potential) becomes equal or until the development of osmotic pressure prevents further movement of water molecules from the solution at lower concentration to that at higher concentration”. Gypsum added to The Clinker in Cements Manufacturing: The clinker is blended and ground with a certain amount of gypsum, CaSO4•2H2O (CŠH2) in percentages about 1.5-5%, whose main function is to avoid a phenomenon known as “flash-set”. Calcium aluminates C3A (unlike calcium sulphate C3S), one of the components of cement, are not amorphous but crystalline and for this reason they are not able to form a protective impermeable layer on the C3A grains surface. So the C3A grains surface go continuous hydration which became uncontrolled after certain time. If such uncontrolled hydration is allowed to occur without taking any precaution, severe

problems can be experienced like “flash set” problem. To avoid this and control the C3A hydration, 1.5-5% of gypsum is regularly added to the cement clinker prior to its final grinding. The gypsum CaSO4•2H2O releases calcium Ca +2 and sulphate SO4-2 ions when contact with water. These ions react with the aluminates and hydroxyls released by the C3A to form a calcium trisulfoaluminate hydrate. Adv/Disdv. of mud circulation at BHA breakage: Adv to remove kick… Disdv – compaction of cutting and everything that is solid.

Maximum pressure allowable at the choke, Pch”. Called also the Maximum Allowable Annular Surface Pressure or MAASP, it represents the maximum pressure that can be allowed to accumulate at the wellhead in case a kick had to be controlled, without causing the fracturing of the formation below the shoe of the last casing run in hole. It is clear that as mud density increases, ΔP ch decreases. Causes of Overpressure: - Compaction disequilibrium – Tectonics – Temperature increase – Diagenesis

Causes of Under pressure: - Osmosis – Diferential discharge – Diferential gas flow – Rock dilatancy – Thermal efect – Prolonged reservoir production F/L Parameters: - Linear Wt, Surface tension, Spe wt on bit - F/V Parameters: - Spe Wt, Press grad, ECD Why KgF/cm2 is better unit: - better than atm, bar, etc because it yields values that are exact and requires no truncations (ie no decimal places) Section of Hydraulic circuit where mud velocity is used to overcome 10m/s: - Nozzle of bit – Drill collar –

Annular spaces available for drill collar and hole. Pressure Units: - lbf/100ft2 < atm < bar < kg/cm2 < psi (or lbf/ft2) < Pa (or N/m2) ROP Variation in SBM formulation: D- ROP for roller cone bit, D+ ROP for PDC bits Zero-D parameter for OBM formulations: - Bingham number Structural disadvantage of CWD tech: - Buckling Kick: -Influx of any formation fluid into the well. This may be due to underbalance ie hydrostatic pressure lower than the formation pressure. Blowout: -loss of control of the well.

What happens to the mud density when drilling restarts: A: The mud density increases momentarily due to 1) Surge operations 2) Pumping restarts because of its: 1. instant gel strength (10 secs) or 2. 10 minutes Gel strength. Mud Thixotropic behavior: a sol-like state when in motion and in a gel-like state when in static conditions (time and dynamics dependent state of viscosity). Bentonite is the additive responsible for this behavior in drilling fluids. Gel Strength: defines the attitude of a fluid to form a gel-like structure, mainly due to the electrostatic interactions of electrically charged products and

chemicals such as bentonite, native clays, shales and polymers. The gel strength indicates the ability of a fluid to maintain the solids in suspension once circulation is stopped and the drilling fluid is in static conditions. Fundamental difference between Plastic and marsh viscosities: 1. Instrumental design & Availability- Plastic is theoretical, Marsh is experimentally derived 2. Physical Parameters- Plastic: pressure x time, Marsh: Time/volume. When have we applied hyperbolic functions during the course? Professor Bourgeons approach to resolve Tension and Bending on drill strings