ch1 casing2.pptx

UNIVERSITI TEKNOLOGI PETRONASPETROLEUM ENGINEERING DEPARTMENT

Chapter 1

Casing

PCB3043 WELL DESIGN & COMPLETION JANUARY 2015

Learning Objectives

• To differentiate casing types

• To describe casing properties and various connection used

• To solve the casing design

• To explain the wellheads and casing hangers


Contents

1.1 Casing string

1.2 Terminology and casing properties

1.3 Wellheads and casing hangers

1.4 Casing design


When was the first well drilled?- Worldwide- Malaysia- PETRONAS

Question 1.2


WorldwideFirst commercial well was drilled in USA in 1859• Drilled by Col Edwin L. Drake

Answer 1.2

PETRONAS First well was for Duyong field in August 1980• Drilled by PETRONAS Carigali Sdn. Bhd.


Answer 1.2

MalaysiaFirst well was drilled in Malaysia was in 1910• Drilled by Shell in Miri (Canada Hill) aka Grand Old Lady


1.1 Casing string

What is casing?Large diameter steel pipe lowered into a borehole and cemented in place

Source: www.steelpipes.org


1.1 Casing string

It is possible to drill a well with a single casing size?

Hydrocarbon


1.1 Casing string

A typical set of casing string

• These pipes are run to different depths

• One or two of them may be omitted depending on the drilling conditions

• They also may be run as liners or in combination of liners

Source: www.nadlcorp.com


1.1 Casing string

Example

Hydro-pressured well

Geo-pressured well


1.1 Casing string

Example

Deepwater Horizon Casing Design (18,360 ft)

Source: www.nola.com


- When we finished the well, what physically leave behind is mainly Casing and cement

- Casing has to maintain the operational functionality and pressure containment that is essential for the entire life of the well

Do you aware of these

Source: frackwire.com


1.1 Casing string

Conductor Casing

• The first casing string to be run and consequently has the largest diameter

• Two methods to run the pipe; In soft area or most offshore environment, the pipe is generally

driven into the ground with a large diesel hammer (drive pipe). This pipe need the have thicker coupling (e.g. RL4S)

In hard rock area, a hole need to be drilled first before the pipe generally set at 150-200ft below the ground level or seabed. Only use normal coupling (e.g. BTC or JVLW)

• Main function is to seal off unconsolidated formation at shallow depth


1.1 Casing string

Conductor Casing

Primary function • To prevent wash out of shallow formations (base of the rig)• To control some type of lost circulation in shallow formationsOther functions• To protect subsequent casing strings from corrosion• To support some of the wellhead load• To provide a fluid conduit to raise the circulating high enough to

return to the pit


1.1 Casing string

Surface Casing

• The first casing string to be run after conductor and generally set at 1000-5000ft below the ground level or seabed

• Sizes of the surface casing vary from 7’’ to 16’’ in diameter, with 10¾’’ and 13⅜’’ being the most common sizes

• It is usually cemented to the surface• Setting depth is important in an area where abnormally high pressure are

expected• If the casing set too high, formations below the casing may not have sufficient

strength to allow well to shut in• This can result the influx to surface around the outside of the casing


1.1 Casing string

Surface CasingPrimary function • Prevent fresh-water sands from being contaminated with drilling mud,

gas, oil or salt water State and federal regulations for the protection of underground

fresh-water reservoirs are usually quite specific about the setting depth of surface casing

Other functions• Maintain hole integrity by preventing cave-in and washout of loose

formations• Minimize lost circulation into shallow, permeable zones• Cover weak zones that are incompetent to control kick –imposed

pressures


1.1 Casing string

Intermediate Casing

Main function is to isolate problematic formations between the surface casing setting depth and the production casing setting depth that prevent the well from being drilled to the target depth• Possible problems;

Sensitive shale Lost circulation zone Abnormal pressure Squeezing salt

• Number of intermediate casing will depend on the number of such problems encountered


1.1 Casing string

Production Casing

• It is either run through the pay zone or set just above it (open hole completion).

• Main purpose is to isolate the production interval from other formation (e.g. water bearing sands) and to act as conduit for production tubing

• It should be thoroughly pressure tested before running the completion since it forms the conduit for fluids to flow.


1.1 Casing string

Liner• A liner is an abbreviated string of casing used to case open hole below

existing casing• It is a short casing string (less than 5000ft) which is suspended from the inside

of the previous casing string by a device known as liner hanger• The liner hanger is attached to the top joint of the liner in the string• It consists of a collar which has hydraulically or mechanically set slips (teeth)

which, after activated, grip the inside of the previous casing• The slips support the weight of the liner and therefore the liner does not have

to extend back up to the wellhead• Liner may be used as intermediate or production string• Liners are often cemented in place, but production liners are sometimes

suspended in the well without cementing


1.1 Casing string

Types of Liner

Casing Liner• Casing liner is a section of casing

that is suspended from the existing casing (surface or intermediate casing)

• In most cases, it extends downward from into the open hole and overlaps the existing casing by 200 to 400 ft

• It is used to isolate abnormal formation pressure, lost circulation zones, heaving shale and salt sections, and to permit drilling below these zones without having well problems


1.1 Casing string

Types of LinerProduction Liner• Production liner is run instead of full casing to provide

isolation across the production or injection zones• In this case, intermediate casing or drilling liner

becomes part of the completion string

Tie back Liner• The drilling liner is often used as part of the production

casing rather running an additional full string of pipe from the surface to the producing zone

• The liner is tied-back or connected to the surface by running the additional pipe required to connect to the liner top


1.1 Casing string

Types of LinerScab Liner• Scab liner is a section of casing used to repair existing

damaged casing.• It may be cemented or sealed with packers at the top

and bottom

Scab Tie-back Liner• This is a section of casing extending upwards from

the existing liner, but which does not reach the surface and normally cemented in place.

• Scab tie-back liners are commonly used with cemented heavy-wall casing to isolate salt sections in deeper portions of the well.


1.1 Casing string

Liner

• Pro/Cons Shorter length of casing string (cost reduction) Liner run on drill pipe (less rig time to run the string) Liner can be rotated during cementing (improve mud displacement and

cement job) Sometimes troublesome due to leakage Disengagement from the run-in string may be difficult or impossible Poor primary cement job due to smaller clearance


1.1 Casing string

Casing String Size


1.2 Casing properties

What is your level?

• API• OCTG• ISO• SMLS• ERW• OD• ID• WT• Csg• Tbg



What is your level?• API- American Petroleum Institute• OCTG- Oil Country Tubular Goods• ISO- International Standardization Organization• SMLS- Seamless• ERW- Electric Resistance Welding• OD- Outer Diameter• ID- Inner Diameter• WT- Wall thickness• Csg- Casing• Tbg- Tubing



• API 5CT:2011 / ISO 11960:2011 (Casing tubing)• API Bulletin 5C2 / TR 5C3 / ISO TR 10400:2007 (Formula)• API 5-CRA:2010 / ISO 13680:2010 (Chrome)• API RP 5C5:2003 / ISO 13679:2002 (Premium connection testing)• NACE MR 0175:2009 / ISO S5156:2009 (Drillpipe)

Standards



Standard- API 5CT History

1st Edition197x

2nd Edition1981(5A, 5AC, 5AX, 5AQ)

3rd Ed 19884th Ed 19925th Ed 19956th Ed 19997th Ed 20018th Ed 2005

9th Edition 2011 (latest)



API 5CT / ISO 11960



API 5CRA / ISO 13860



OCTG Tubular Classification1. Manufacturing Type

Determines its manufacturing method

2. Size Indicates its nominal OD Imperial unit- “inch” SI unit- “mm” is uncommon except in certain places like China or Japan

3. Weight Imperial unit- “pound per foot” or “lbs/ft” or “#” SI unit-”kg/m” is rare but exists in certain places

4. Grade Strength & type of material (carbon steel, low alloy steel, stainless steel) Two main grades- API or Proprietary grades

5. Connection Type of connection to be threaded on the pipe ends Two main grades- API and Proprietary premium connections


1.2 Casing propertiesOCTG Tubular Classification

1. Manufacturing TypeSeamless or Electric Resistance Welding (ERW)

2. Size 1.050” to 20” 1.050” to 1.900” (macaroni tubing) 2 3/8” to 4 ½” (tubing) 5” to 16” (casing) 18 5/8” to 36” (conductor)

3. Weight Light to heavy wall thickness (indicates weight) Example: 7” 23# to 42.7#

4. Grade Strength, in terms of KSI (e.g. K55, L80, P110, SM13CRS-110, SM2731) Corrosion (e.g. carbon steel, 13%Chrome, Duplex, Nickel based alloy)

5. Connection API connection- BTC, EUE, 8rd, LTC, STC Premium connection- VAM, JFE, and others



1. OCTG-Manufacturing TypeTwo basic processes• Seamless pipe

Seamless pipe is a wrought steel pipe manufactured by a seamless process.

A billet is pierced by a mandrel and the pierced tube is subsequently rolled and re-rolled until the desired diameters are obtained

• Welded pipe - Electric Resistance Welding (ERW) and UO In the electric welding processes, flat sheet

stock is cut and formed, and the two edges are welded together by electric flash or electric resistance welding without adding extraneous metal.



1. OCTG-Manufacturing Type

Large OD pipe cannot be made by seamless process



1. OCTG-Manufacturing TypeSeamless Pipe Welded Pipe (ERW & UO)

Pros • Good quality (less defects)• Wide variety of material

grade

• Relatively cheaper• Excellent dimensional accuracy (good

for expandable tubular)• Better availability

Cons • Relatively expensive• Limited availability• Lack dimensional accuracy

• Quality concern on weld-seam (risk of leak & burst, not suitable for sour service)

• Inhomogenous mechanical property• Limitation of YS (80-110)• Carbon steel only (CRA cannot be

welded)

Summary • Production casing • tubing

• Conductor, surface and intermediate casing

• Expandable tubular



• API specifications simplify the selection and purchase of steel tubular for most applications

• API grades designation consist of a letter and a number

P-110Arbitrarily selected, but at one time used to uniquely defined a specific grade-still used to distinguish between grades

Specifies the Minimum Yield Strength (MYS) of tubular materials in KSI or ‘000 psi

4. OCTG-GradeStrength-API 5CT



4. OCTG-Grade

• Manufacturers (steel mills) also provide proprietary grades which are not governed by API specifications but of better performances

• It may have improved properties High toughness at higher yield strength Toughness at ultra low temperature (artic grade) SSC resistance Higher collapse resistance (High collapse grade) Anti-corrosion performance against CO2/H2S/Cl- (CRA grade)

• Achieved by more stringent controls on certain manufacturing processes (typically higher cost)

• Manufacturer’s claim should be supported by extensive testing or have been accepted by industry standards

Strength-Proprietary



4. OCTG-Grade

• Basic Steel - (covered in 5CT) Carbon steel (CS) - all API grades Low Alloy Steel (LAS) - <5% alloying - API and Proprietary grades

• Corrosion-Resistance Alloys (CRA) – (covered in API 5CT and API 5CRA) Martensitic Stainless steel (MSS) Duplex Stainless steel (DSS) Nickel-based alloy (NI-based) - mostly proprietary grade

Material



5. OCTG-Connection• Connection is to couple two ends of the pipes. It needs to sustain

high tensile load, to provide pressure containment.• Two ends: Pin and Box

PinBox



5. OCTG-Connection• Connection is to couple two ends of the pipes. It needs to sustain

high tensile load, to provide pressure containment.• Two groups: API connection and Premium Connection Threaded and Coupled (T&C) –

with coupling Integral joint (IJ) –

without coupling -Semi flush Full flush



5. OCTG-Connection

• Thread Form (shape of the thread) Taper

change in diameter of a thread

Height Distance between the crest and the root of a thread measured normal to the axis of the thread

Connection Design



5. OCTG-Connection

• Thread Form (shape of the thread) Lead

distance from one point on the thread to the corresponding point on the adjacent thread and is measured parallel to the thread axis

Pitch Diameterdiameter of an imaginary cone that bisects each thread midway between its crest and root

Connection Design



5. OCTG-Connection

• Thread Seal – a joint must prevent the leakage of the fluid/gas Thread dope seal

gaps between the roots and crests and between the flanks of the mating surfaces are plugged by a thread compound (containing powered metals, also provide lubrication)

Metal to metal sealapplying a makeup torque sufficient to wedge the pin and box together and cause interference between the thread elements

Connection Design



5. OCTG-Connection

• Tubular connection Connection Design

Threaded connection Welded connection

Description • Thread form on pipe ends • External connector welded on the pipe body

Summary • Thread damage during alignment of joints

• Thread damage due to excessive torque

• Relatively slow make up times of large diameter pipe

• Strength related to casing/pipe grade

• Limited tensile & pressure capacity

• Allowed for increased stabbing/alignment characteristic

• Connector material was independent prom pipe grade

• Increased internal pressure and bending load capacity

• Less prone to thread damage from excessive torque



5. OCTG-Connection

• Joint efficiency (tensile strength of the joint divided by the tensile strength of the pipe) Jump out: separation of pin and box without damage to the thread

element Fracture: threaded section separates from the pipe body Thread shearing: stripping off of thread from the pin/box

Connection Design



5. OCTG-Connection• API Connections

Pipe Connection Upset Thread Form

Tubing

Non-Upset Threaded & Coupled (NUE) Not required

Round TubingExternal-Upset Threaded and Coupled (EUE) Required

Integral Joint (IJ) Required

Casing

Short Round Thread (STC) Not requiredRound Casing

Long Round Thread (LTC) Not requiredButtress Thread (BTC) Not required

ButtressExtreme-Line Thread Required



5. OCTG-Connection• API Connection (Tubing) – NUE & EUE

NUE EUE



5. OCTG-Connection• API Connection (Tubing) – IJ



5. OCTG-Connection• API Connection (Casing) – STC & LTC



5. OCTG-Connection• API Connection (Casing) – BTC & X-Line

BTC X-Line


Question

Which one?- Drilling Rig- Production unit- Platform

A

B

C


A

B

C

Answer

Production unit

Platform

Drilling Rig



4. OCTG-Connection• Premium Connection• Features

Metal to metal seal Torque shoulder ID flush profile Improved thread design



4. OCTG-Connection• Premium Connection

Metal to metal seal Torque shoulder ID flush profile Improved thread design



Casing Classification

No Criteria Example

1 Outside diameter 13 3/8”

2 Material Grade L-80

3 Nominal weight 47lb/ft

4 Wall thickness 0.5”

5 Type to threads and couplings API LCSG

6 Length of each joint (RANGE) RANGE 3



Casing Loads• There are different types of loads exerted on casing during

landing, cementing, drilling and production operations• The most important loads on casing as specified by API

1. Tensile2. Burst3. CollapseThe most important loads on casing as specified by API

• The other loads are compression, wear, corrosion, vibration and pounding by drillpipe, effects of gun perforating and erosion.



Joint strength minimum tensile force required to cause joint to failure

1. Casing Loads-Tensile

Yield strength

tensile stress required to produce a total elongation of determined percentage of the gauge length (e.g. 0.5%)

Tensile load < min (Joint strength, casing body yield strength)




• Sources of tension loads1. Suspended weight of casing string2. Bending force3. Shock load4. Pressure testing




• Suspended weight – effective weight of the pipe is reduced after immersed in drilling fluid due to buoyancy effect

h𝑊𝑒𝑖𝑔 𝑡 𝑖𝑛𝑎𝑖𝑟 ,𝐹 𝑎𝑖𝑟 (𝑙𝑏)=𝑁𝑜𝑚𝑖𝑛𝑎𝑙 h𝑤𝑒𝑖𝑔 𝑡 ( 𝑙𝑏𝑓𝑡 )×𝑝𝑖𝑝𝑒 h𝑙𝑒𝑛𝑔𝑡 ( 𝑓𝑡 )

𝐵𝑢𝑜𝑦𝑎𝑛𝑡 h𝑤𝑒𝑖𝑔 𝑡 ,𝐹 𝑒=𝐹 𝑎𝑖𝑟×𝐵𝑢𝑜𝑦𝑎𝑛𝑐𝑦 𝑓𝑎𝑐𝑡𝑜𝑟 ,𝐵𝐹

𝐵𝐹=1−𝑠𝑝𝑒𝑐𝑖𝑓𝑖𝑐 h𝑤𝑒𝑖𝑔 𝑡 𝑜𝑓 𝑑𝑟𝑖𝑙𝑙𝑖𝑛𝑔 𝑓𝑙𝑢𝑖𝑑 (

𝑙𝑏𝑔𝑎𝑙

)

𝑠𝑝𝑒𝑐𝑖𝑓𝑖𝑐 h𝑤𝑒𝑖𝑔 𝑡 𝑜𝑓 𝑠𝑡𝑒𝑒𝑙(65.4 𝑙𝑏𝑔𝑎𝑙

)where




Calculate the suspended weight of 7000ft, L-80/47lb/ft casing string in 12.5ppg mud 𝐹 𝑎𝑖𝑟=47

𝑙𝑏𝑓𝑡×7000 𝑓𝑡=329,000 𝑙𝑏

𝐹 𝑒=329 ,000 𝑙𝑏×0.809=266,161 𝑙𝑏

𝐵𝐹=1−12.5

𝑙𝑏𝑔𝑎𝑙

65.4𝑙𝑏𝑔𝑎𝑙

=0.809

• Suspended weight

Example



1. Casing Loads-Tensile• Bending force – casing is subjected to bending forces when run in a

deviated well. The lower surface of the pipe stretches and is in tension. The upper surface shortens and is in compression

𝐹 𝑏 (𝑙𝑏)=63𝑑𝑜𝑊𝑛𝜃where

7” L-80/47lb/ft casing in a borehole of 3o/100ft dogleg severity

Example

𝐹 𝑏=63 (7 ) (47 ) (3 )=62,181𝑙𝑏



1. Casing Loads-Tensile• Shock load – while running the casing, it is subjected to acceleration

loading by setting of the slips and application of hoisting brakes𝐹 𝑠 (𝑙𝑏)=3200𝑊𝑛

𝑉 𝑠=𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 𝑜𝑓 𝑠𝑡𝑟𝑒𝑠𝑠𝑤𝑎𝑣𝑒 𝑓𝑜𝑟 𝑠𝑡𝑒𝑒𝑙 (17 028 𝑓𝑡 / 𝑠)where

𝐹 𝑠 (𝑙𝑏)=2𝛾 𝑠𝑉 𝑝𝑉 𝑠 𝐴𝑠

𝑔

(3.04ft/s)

𝛾𝑠=489.5 𝑙𝑏 / 𝑓𝑡3

𝑔=32.17 𝑓𝑡 /𝑠2

𝐴𝑠=𝑊𝑛(

𝑙𝑏𝑓𝑡

)

3.46 𝑖𝑛2

¿



1. Casing Loads-Tensile• Shock load

𝐹 𝑠=3200×47×139

=217,250 𝑙𝑏

𝐹 𝑠=( 2×489.532.17 )×( 409 )×17,208×( 473.46 )×( 1144 )=217,250 𝑙𝑏

Example

Consider sections of L-80, 47lb/ft casing being run into the borehole at an average rate of 9s per 40ft. Calculate the shock load if the casing is moving at its peak velocity when the slips are set

The is based on 3.04ft/s (13s per 40ft). Thus,

The peak running speed is twice the average, so the shock load is

(𝐹 𝑠 )𝑝𝑒𝑎𝑘=217,250×2=434,500 𝑙𝑏




• Pressure testing – often carried out prior to drilling the float collar and float shoe for the purpose of leakage check. During pressure testing, extra tensional load is exerted on each section.

𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒𝑡𝑒𝑠𝑡𝑖𝑛𝑔 (𝑙𝑏 )=60%𝑜𝑓 𝑏𝑢𝑟𝑠𝑡𝑟𝑒𝑠𝑖𝑠𝑡𝑎𝑛𝑐𝑒×𝑖𝑛𝑡𝑒𝑟𝑛𝑎𝑙𝑎𝑟𝑒𝑎𝑜𝑓 𝑐𝑎𝑠𝑖𝑛𝑔

Example

Calculate tension load due to pressure testing on a 7” L-80/38lb/ft casing. (ID = 5.92in, burst resistance = 8,460psi)

𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒𝑡𝑒𝑠𝑡𝑖𝑛𝑔 (𝑙𝑏 )=0.6×8460×( 𝜋4 ×5.922)=139,719 𝑙𝑏




𝑻𝒐𝒕𝒂𝒍𝑻𝒆𝒏𝒔𝒊𝒍𝒆 𝑳𝒐𝒂𝒅=𝑆𝑢𝑠𝑝𝑒𝑛𝑑𝑒𝑑 h𝑤𝑒𝑖𝑔 𝑡+𝑏𝑒𝑛𝑑𝑖𝑛𝑔 𝑓𝑜𝑟𝑐𝑒+𝑚𝑎𝑥( h𝑠 𝑜𝑐𝑘𝑙𝑜𝑎𝑑 , 𝑡𝑒𝑛𝑠𝑖𝑜𝑛𝑑𝑢𝑒𝑡𝑜𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒𝑡𝑒𝑠𝑡𝑖𝑛𝑔)𝑺𝒂𝒇𝒆𝒕𝒚 𝒇𝒂𝒄𝒕𝒐𝒓 𝒇𝒐𝒓 𝑻𝒆𝒏𝒔𝒊𝒐𝒏=

𝑚𝑖𝑛(𝑐𝑎𝑠𝑖𝑛𝑔 𝑦𝑖𝑒𝑙𝑑 h𝑠𝑡𝑟𝑒𝑛𝑔𝑡 , 𝑗𝑜𝑖𝑛𝑡 h𝑠𝑡𝑟𝑒𝑛𝑔𝑡 )𝑡𝑜𝑡𝑎𝑙𝑡𝑒𝑛𝑠𝑖𝑜𝑛𝑙𝑜𝑎𝑑

• Safety factor for tension should be



2. Casing Loads-Burst• Sources of tension loads

1. Column of drilling fluid acting on the inside wall of the pipe2. Kick imposed burst pressure if a kick occurs during drilling

operations• Based on API, the burst pressure resistance;

𝑃𝑏𝑟=0.8752𝜎 𝑦

(𝑑𝑜/𝑡 )

𝜎 𝑦=𝑦𝑖𝑒𝑙𝑑 h𝑠𝑡𝑟𝑒𝑛𝑔𝑡 𝑜𝑓 𝑝𝑖𝑝𝑒 (𝑝𝑠𝑖 )𝑑𝑜=𝑛𝑜𝑚𝑖𝑛𝑎𝑙𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟 𝑜𝑓 𝑝𝑖𝑝𝑒 (𝑖𝑛)𝑡=𝑝𝑖𝑝𝑒𝑤𝑎𝑙𝑙 h𝑡 𝑖𝑐𝑘𝑛𝑒𝑠𝑠(𝑖𝑛)

where

API allows 12.5% manufacturer’s tolerance in the nominal wall thickness



2. Casing Loads-Burst

Calculate the burst rating of 9 5/8” N-80/47lb/ft casing given that the wall thickness is 0.472”

𝑃𝑏𝑟=0.8752 (80,000 )

(9.652/72 )=6,865.5𝑝𝑠𝑖

Example



3. Casing Loads-Collapse• Sources of tension loads

1. Hydrostatic head of the fluid column (mud & cement slurry) outside the casing

2. Deformation of rocks (shale & salts)• Strength of casing under external pressure depends on

Length Diameter Wall thickness Physical properties of the casing material (yield point, elastic

limit, young’s modulus, poisson’s ratio ect) Axial loading



3. Casing Loads-Collapse• Casing failure models under collapse pressure

Casi

ng st

reng

th

Wal

l thi

ckne

ss (d

o/t) Yield strength collapse

Plastic collapse

Transition collapse

Elastic collapse


1.3 Wellhead & HangersWellhead & Casing hanger

• All casing are suspended from a wellhead by using casing hanger. For onshore and offshore platform, the wellhead is just below the rig floor

• For drilling offshore on a floating vessel, wellhead is installed at the seabed• Main functions: to suspend the weight of the casing string, to seal off the

annulus between successive casing string, as interface between the casing and BOP stack.

• Two types of wellhead; Spool - require different set of spool for different casing sizes - many seals (increase chances of pressure leak) - BOP must be removed to install next casing spool Compact spool - enable several casing strings to be suspended from a single spool


1.3 Wellhead & HangersWellhead & Casing hanger

• Two types of wellhead; Spool - require different set of spool for different casing sizes - many seals (increase chances of pressure leak) - BOP must be removed to install next casing spool Compact spool - enable several casing strings to be suspended from a single spool

• Two types of casing hanger; Mandrel Slip type


References

Fundamentals of casing designBy Hussain Rabia

Drilling EngineeringBy Jamal J. Azar, G. Robello Samuel

Drilling Technology in Nontechnical LanguageBy Steve Devereux

Casing Design - Theory and PracticeBy S.S. Rahman & G.V. Chilingarian

Casing and Cementing, 3rd Ed.

Casing and Liners for Drilling and CompletionBy Ted G. Byrom


1.4 Casing Design

The selection of• Casing setting depth• Casing sizes• Grades of steel

Controlling factors• Geological conditions• Hole problems• Number and sizes of production tubing• Stock availability• Downhole production equipments• Company policy etc.

Casing program design involve


1.4 Casing Design

Maximum load criteria• Casing string is designed to withstand the worst load

conditions associated with drilling & production operations Most economic criteria

• Combination string with multiple sections of different steel grades, wall thickness and coupling types

Criteria


1.4 Casing Design

Conductor casing

• No formula available since too many variables and complexity

• Shallow well with hard surface soil (50-100ft) while soft formation (200-250ft)

• In absence of soil data, just do what everyone else does (similar depth or deeper)

• If critical well, get the soil data

Casing Setting Depth

Surface casing

• Consider some factors (choose the deepest depth) Pore pressure Fracture pressure Depth of freshwater zone Legal regulations


1.4 Casing Design

Intermediate casing

• Consider critical issues Mud density Overpressure Presence of unstable and corrosive zones


Production casing

• Type of completion

• Fluid types

• Producing zone depth


Well depth (ft)

Pore pressure EMW (ppg)

Fracture pressure EMW (ppg)

0 8.95 10.8

1000 8.95 11.2

2000 8.95 11.65

3000 8.95 12.7

4000 8.95 13.2

5000 8.95 13.35

6000 8.95 13.6

7000 8.95 14.2

8000 10.0 15.0

9000 11.45 15.55

10000 12.35 15.85

11000 13.30 16.15

12000 14.0 16.45

13000 14.45 16.75

13500 14.7 16.9

1.4 Casing Design



At 10000ft

𝑃𝑜𝑟𝑒𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒=12.35 x 0.052 x10000=6422 psi

𝐹𝑟𝑎𝑐𝑡𝑢𝑟𝑒𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒=15.85 x 0.052x 10000=8242 psi

𝑃𝑜𝑟𝑒𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑔𝑟𝑎𝑑𝑖𝑒𝑛𝑡=12.35 x 0.052=0.6422 psi / ft

𝐹𝑟𝑎𝑐𝑡𝑢𝑟𝑒𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒𝑔𝑟𝑎𝑑𝑖𝑒𝑛𝑡=15.85 x 0.052=0.8242 psi / ft

1.4 Casing Design


1. Apply trip margin to pore pressure and kick margin to fracture gradient

2. Determine primary setting depth for each casing string based on pore pressure and fracture gradient

3. Check for the likelihood of pipe-sticking due to differential pressures for each casing string, adjust casing setting depth if necessary

4. Check for kick imposed pressure at surface casing shoe, adjust surface casing setting depth if necessary

1.4 Casing Design



1. Apply trip margin to pore pressure and kick margin to fracture gradient

1.4 Casing Design


2. Determine primary setting depth for each casing string based on pore pressure and fracture gradient

1.4 Casing Design


3. Check for the likelihood of pipe-sticking due to differential pressures for each casing string, adjust casing setting depth if necessary

∆ 𝑃=𝐷𝑥 (𝜌𝑚−𝜌 𝑓 ) 𝑥 0.052∆ 𝑃=𝑑𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑡𝑖𝑎𝑙𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 ,𝑝𝑠𝑖𝜌𝑚=𝑠𝑝𝑒𝑐𝑖𝑓𝑖𝑐 h𝑤𝑒𝑖𝑔 𝑡𝑜𝑓 𝑑𝑟𝑖𝑙𝑙𝑖𝑛𝑔 𝑓𝑙𝑢𝑖𝑑 ,𝑝𝑝𝑔𝜌 𝑓=𝑠𝑝𝑒𝑐𝑖𝑓𝑖𝑐 h𝑤𝑒𝑖𝑔 𝑡 𝑜𝑓 𝑓𝑜𝑟𝑚𝑎𝑡𝑖𝑜𝑛 𝑓𝑙𝑢𝑖𝑑 ,𝑝𝑝𝑔

Differential pressure for intermediate casing

Normal pressure zone, 8.95 ppg ends at 7000 ft. The intermediate casing setting depth is 9500 ft, 12.4 ppg

ok

Differential pressure for production casingok

1.4 Casing Design


4. Check for kick imposed pressure at surface casing shoe, adjust surface casing setting depth if necessary

𝑃𝑘

𝐷𝑠

=0.052𝑥 0.5( 𝐷𝑖

𝐷𝑠)+𝐺𝑝𝑓

∆ 𝑃=𝑘𝑖𝑐𝑘𝑖𝑚𝑝𝑜𝑠𝑒𝑑𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒𝑎𝑡 𝐷𝑠 ,𝑝𝑠𝑖𝐷𝑠=𝑠𝑒𝑡𝑡𝑖𝑛𝑔 h𝑑𝑒𝑝𝑡 𝑓𝑜𝑟 𝑠𝑢𝑟𝑓𝑎𝑐𝑒𝑐𝑎𝑠𝑖𝑛𝑔 , 𝑓𝑡𝐷𝑖=𝑠𝑒𝑡𝑡𝑖𝑛𝑔 h𝑑𝑒𝑝𝑡 𝑓𝑜𝑟 𝑖𝑛𝑡𝑒𝑟𝑚𝑒𝑑𝑖𝑎𝑡𝑒𝑐𝑎𝑠𝑖𝑛𝑔 , 𝑓𝑡

𝐺𝑝𝑓= 𝑓𝑜𝑟𝑚𝑎𝑡𝑖𝑜𝑛 𝑓𝑙𝑢𝑖𝑑𝑔𝑟𝑎𝑑𝑖𝑒𝑛𝑡𝑎𝑡 𝐷𝑖 ,𝑝𝑠𝑖 / 𝑓𝑡

At 𝑃 𝑘

3500=0.052𝑥0.5 ( 95003500 )+11.9𝑥0.052=0.689𝑝𝑠𝑖 / 𝑓𝑡

Kick imposed pressure<fracture gradient !

Depth (ft) Kick imposed pressure gradient (psi/ft)

Fracture pressure gradient (psi/ft)

3500 0.689 0.673

4000 0.681 0.686

5000 0.668 0.689Surface casing

at 5000ft

1.4 Casing Design


Final setting depth

1.4 Casing Design


1.4 Casing Design


• Production Tubing string Production rate and frictional pressure loss Nodal analysis

• No of casing string

• Drilling conditions Bit size/drift diameter Borehole and hole cleaning Cementing requirement

- annular clearance on 0.375” is sufficient (0.75 is preferable) for cement to hydrate and strength development

1.4 Casing Design

Casing & Hole Size

ch1 casing2.pptx

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