PETE 225 Casing and Casing Design
A finished, deliverable product • As a drilling drilling engineer, you will will deliver a wellbore that is properly placed which has the integrity to proceed with completion and production operations. • Failure to deliver the preceding is a failure at your job. job.
Casing Functions • Hole stabilization stabilization • Protection of fresh water • Zonal Isolation
Casing Functions • Contain Pressure • Environment for subsurface equipment • Enhance the probability reaching TD
Tubing Functions • Conduit for formation fluids • Protects production casing from produced fluids
Tubing Functions
Protects production casing from excessive pressures Protects casing from wear from rod pumps, etc.
Casing Types/Depths TYPE • Drive pipe or structural casing
DEPTH
DIAMETER
150-300’BML 16”-60” • 150-3
• Conductor
• 40’40’-1600’
16” 16”-48”
• Surface
• 100-4 100-4000’
8 5/8”-20 7 5/8”5/8”-13 3/8”
• Intermediate • Production • Liners
• TD
2 7/8”7/8”-9 5/8”
Drive Pipe/Conduc Pipe/Conductor tor • Drive pipe
Provides a means of nippling up diverters Provides a mud return path Prevents erosion of ground below rig
• Conductor pipe
Same as Drive pipe
Isolates very weak formations
Allows drilling of surface hole without wellbore collapsing
Surface Casing
Provides a means of nippling up BOP Provides a casing seat strong enough to safely close in a well after a kick. Provides protection of fresh water sands Provides wellbore stabilization Supports weight of subsequent casing strings.
Intermediate Casing
Provides isolation of problem formations Provides integrity to withstand the high mud weights necessary to reach TD or next csg seat
Production Casing
Provides zonal isolation Confines production to wellbore Provides the environment for subsurface completion completion equipment
Drilling Liner
Same function as intermediate casing Does not return to surface
Production Liner
Same function as production casing Does not return to surface
Tie-back Liner
Come back at a later date and convert liner into a full string Runs from top of liner to surface
Casing Properties • Outside diameter Weight/foot • Wall thickness • Connection • Inside diameter
Nominal ID Drift diameter
Casing Grade
Running Casing • Offload casing (in order) • Tally/strap and drift casing • Inspect and clean threads
All rights reserved © 2008 PETEX ® (Petroleum Extension Service), The University of Texas
All rights reserved © 2008 PETEX ® (Petroleum Extension Service), The University of Texas
Running Casing • Pickup 1st joint • Install guide/float shoe and collar on shoe track.
All rights reserved © 2008 PETEX ® (Petroleum Extension Service), The University of Texas
All rights reserved © 2008 PETEX ® (Petroleum Extension Service), The University of Texas
All rights rights reserved reserved © 2008 PETEX PETEX ® (Petroleum Extension Service), The University of Texas
All rights reserved © 2008 PETEX ® (Petroleum Extension Service), The University of Texas
Running Casing • Pickup casing joint • Install any centralizers, etc.
All rights reserved © 2008 PETEX ® (Petroleum Extension Service), The University of Texas
All rights reserved © 2008 PETEX ® (Petroleum Extension Service), The University of Texas
Running Casing • Stab joint (pin into box) • Install fillup tool, latch elevators
All rights reserved © 2008 PETEX ® (Petroleum Extension Service), The University of Texas
• Pull slips, slips, run run casing casing to rig floor • Set slips All rights reserved © 2008 PETEX ® (Petroleum Extension Service), The University of Texas
• Pickup Pickup next next joint joint and and repea repeatt to setting depth
Running Casing: CRT/top drive CRT (casing running tool) • Eliminates man in derrick • Can circulate and rotate casing (in event of problems). Top Drive only:
Casing Running Tool
• May use links/bails (arms) on top drive to steady and move casing while RIH even if no CRT used.
Weatherford International
Sequence of drilling a well
Casing Depths Casing point
Once equivalent mud weight becomes less than pore pressure EMW or greater than fracture gradient EMW: set casing
Casing point
Stresses on casing DESIGN FOR:
Typical Design Factors
• Burst Burst - Intern Internal al pressu pressure re
• Burst - 1.1
• Colla Collaps pse e - Exte Extern rnal al pressure
Collap apse se - 1.12 1.125 5 • Coll
• Tens Tensio ion n - from from the the weight of the casing itself trying to pull the casing apart
• Ten Tension sion - 1.8
Burst • Design for maximum pressure on the inside of the casing.
Frac Frac breakd breakdown own pressu pressure re on toe perf perfs s
Kick after running casing
Other – Other – may be area/company dependent
Do you assume “backup” pressure?
• Burst strength can be increased through tension – tension – usually ignore this effect.
Burst failure
Collapse • Typically assume no backup pressure inside casing • Standard scenario is hydrostatic column on outside and vacuum on inside. tension – • Collapse rating is reduced with tension – this may be accounted for in certain situations.
Collapse failure
Tension • API recommendations recommendations call for worst case, where there is no buoyancy effect. Design is based on the weight of the entire casing string.
Tensile failure
Burst and collapse calculations • HSP = 0.052 x MW, ppg x TVD, ft • For Production casing set at 15,000
Burst is anticipated formation pressure at 15,000’
Collapse is calculated for MW at 15,000
MW is 18 ppg
Pore Pressure is 17.2 ppg
Maximum tool/bit OD through this casing string is 4.50 inches.
Pressure requirements • Burst 0.052 x 17.2 x 15,000 x 1.1 (D.F.) = 14,758 psi
• Collapse .052 x 18 x 15,000 x 1.125 = 15,795 psi
For collapse, we need at least 15,795 psi rating:
Not Available
For burst, we need 14,758 psi from bottom to top
Designing for Tensile Loads – Casing Design • Tension is the axial strain on a joint or connection.
Static – Static – weight of casing
Dynamic – Dynamic – running in or pulling out of hole
• API standards:
Design/safety Design/safety factor of 1.8
Use air weight of casing
• Finding the casing
eRedbook – eRedbook – Joint Strength (1000 lbs) column
Casing Design: Simplifying assumptions for PETE 225 • Burst – Burst – maximum pore pressure at TD or max frac pressure Collapse – maximum annular hydrostatic pressure at • Collapse – TD resulting resulting from drilling fluid prior prior to pumping cement. • Design for conditions when casing is on bottom. • Casing is run “closed“closed -ended” with a float or check valve on the end.
Annular fluids are forced up the annulus annulus as casing casing enters the wellbore. Casing will be filled at various intervals as it is RIH.
**These Thes e are are as as s umpt umptions ions to help help you s tart lea learning rni ng the cas cas ing des des ig n conce c oncept pt – the real world ca c an and will wi ll be more c ompli ompli c ated* ated** *
Casing Design: Real World Design Criteria •
Pore Pressure
•
Thermal effects of hydraulic fracture treatment
•
Production fluid gradient
•
Thermal effects of production
•
Production fluid type
•
Sand production from formation
•
Artificial lift (multiple types over time)
•
Hydraulic fracture treatment rate
•
Drift needed
•
Hydraulic fracture treatment pressure
•
Wear on intermediate strings while drilling
•
Loads (tri-axial) of running casing in the hole
•
Bending stresses at connections (directional wells)
•
Rotated or reciprocated during cement job
•
Handling IP as well as end of life low flow rates.
•
Rotated into the hole or not
•
Behind-pipe pay
•
•
Centralization
•
Breakdown of cement over time
•
Company and/or regulatory agency regulations
•
Torque turning, casing crews, inspection nee
•
Buckling (pre and post installation)
•
•
Annular pressure buildup
Anticipated initial quality of cement job
Availability
•
Possibility of changing well to injection well
•
Tectonic related casing collapse
•
Loads while installing wellhead
•
Hydrate prevention
•
Loads while cementing
•
Rig capabilities (length, hookload, storage)
•
Cost of casing (materials, delivery, delivery, storage)
•
Anticipated maintenance maintenance via workovers workovers
•
Cost of installation
•
Anchored tubing movement movement
•
Formation subsidence
•
Salt zone encroachment
•
Corrosive formation or fluids
Examples of some of the factors you may take into consideration while designing a casing string.
A finished, deliverable product • How you drill a well is ultimately ultimately of little concern concern to a company. company. What you deliver deliver is of great concern. concern. • As a drilling drilling engineer, you will will safely deliver, on time and under cost, cost, a wellbore that is properly placed which has the required integrity to proceed with completion and production operations.
