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Casing design
- 1. Lecturer Syed Nawaz Free LanceNDT Inspector Founder of Petroleum Universe
- 2. Introduction Functionsof Casing Casing Types Approach to Casing Design Numerical Zone Conclusion References
- 3. Hussain.et.al inFundamentals of Sustainable Drilling says that if a tubular is less 4.5 inch of diameter then it is tubing. The range of casing diameter is 4.5” to 36” Once the section of subsurface is drilled, it has to be cased with steel pipe, which is said to be Casing The reason behind the circular shape of casing is even distribution of pressure Casing constitute 20-30% of the total cost of the well.
- 4. Casing isinstalled to prevent the following problems: ◦ Faults ◦ High pressure formations ◦ Toxic materials ◦ Thief zones, etc
- 5. To protectnear surface unconsolidated formations Provide protection against shallow gas flows Seal off shallow water zones Prevent caving of weak formations Provide protection against shallow blowouts It will ensure that formations at the casing shoe will not fracture at the high hydrostatic pressure which may encountered at later stage. Is usually set in the transition zone below or above an over-pressured zone To seal off a severe loss zone To isolate producing zones, To provide reservoir fluid control To permit selective production in multizone production To isolate lost circulation or abnormally pressured zone
- 6. It preventscross channeling between two or more subsurface fluid bearing layers To provide structural support for the wellhead and BOPs Note: Casing, Tubing, Drill Pipe must all confirm to API series 5 “Tubular Goods” including API Spec, ISO Specifications, etc
- 7. Stove Casing Conductor Casing Surface Casing Intermediate Casing Production Casing Liner Casing
- 8. These aremarine conductor or foundation pile for offshore drilling It is run to prevent washout of near surface unconsolidated formations, to provide a circulation system This pipe does not carry any weight from the wellhead equipment and can be driven into the ground or seabed The normal size for a stove pipe ranges from 26 in to 42 in
- 9. Largest diameter Protect near surface unconsolidated formations, seal off shallow water zones Size vary from 16 inch to 48 inch Conductor pipe is always cemented up-to the surface.
- 10. Prevent cavingof weak formations at shallow depths Shallow blowouts Depth of surface casing depends on aquifers and well head pressure Diameter range is 18.625 to 20 inch in North Sea Operations and casing size in middle east is usually 13.375
- 11. Usually setin the transition zone below or above an over- pressured zone Mainly design to overcome the problems like caving shale, thief zones, mobile salt zones It ranges from 7.625 to 13.375 but no specific range of length
- 12. Last casingplaced at the top of pay zone. Isolate producing zone Range is of 4.5, 5, 7 inches in O.D
- 13. Do notreach the surface Mounted on liner hangers installed to previous casing string (Intermediate Casing). In liner completions both the liner and the intermediate casing act as the production string. The design criteria for liner is usually the ability to withstand the maximum expected collapse pressure
- 16. Design process ◦Selection of Casing Sizes ◦ Selection of setting depths ◦ Definition of design properties Design properties ◦ Collapse pressure ◦ Burst pressure ◦ Yield strength: tensile and compressive ◦ Biaxial loading consideration ◦ Effect of Bending Design procedure ◦ Collapse pressure calculation ◦ Burst pressure calculation ◦ Tensile/ compressive strength calculation Safety factor
- 19. Collapse ◦ Minimumexternal pressure required for pipe collapse (no internal pressure or loads)
- 20. Based ondiameters and thickness there are 4 different types of collapse pressure The API bulletin 5C3 3 reports four formulas for calculating the collapse resistance of tubular goods and they are as follows: ◦ Elastic Collapse Pressure ◦ Transition Collapse Pressure ◦ Plastic Collapse Pressure ◦ Yield Strength Collapse Pressure
- 21. ◦ Yield Strength(x<15.545) ◦ Plastic (15.545 < x < 26.025) ◦ Transition (26.025 < x < 39.9) ◦ Elastic (x > 39.912)
- 22. Under fieldconditions, a given casing section will be under the combined action of external and internal pressure and axial load due to its own weight
- 23. Minimum internalpressure at which pipe permanently deformed (pipe is to no or less external pressure or axial loads) API Burst is given as Lame equation is also used for burst pressure Wall-thickness correction factor 0.875 for standard API tubulars when a 12.5% wall-thickness tolerance is specified.
- 25. The abilityof a metal to tolerate gradual progressive force without any permanent damage or deformation. Classified into 2 pressures or loading: Axial Load and Compressive Load Applying force on a structure directly along the structure axis
- 27. API DesignFactors Forces Range (Globally used) Collapse 1.0-1.125 (1.125) Tension 1.0-2.0 (1.8) Burst 1.0-1.33 (1.1) Triaxial 1.25
- 28. Casing Size Connections Weight Grade Length
- 29. The ODis recognized as the size of Casing. The size of casing vary from 4.5” to 36” Drift Diameter: allowable diameter for next coming tool Breaking out the sequence then factors are to be estimated such as ◦ Connections ◦ Mud weight ◦ Cementing ◦ Dogleg severity
- 31. Pipe weightis usually expressed as weight per unit length in lb/ft. Weight Outer dia Inner dia Wall thickness Drift dia lb/ft in in in in 53.5=1658 9.625 8.535 0.545 8.379 47= 1457 9.625 8.681 0.472 8.525 43.5 =1348 9.625 8.755 0.435 8.599 40 = 1240 9.625 8.835 0.395 8.679 31
- 32. The steelgrade of the casing relates to the tensile strength of the steel from which the casing is made Grade is a dependent property (Chemical Composition, Mechanical Properties) The steel grade is expressed as a code which consists of a letter and a number
- 33. API Casinglength ranges Most commonly used are R-2 Ranges Ranges of Length (ft) Average Length (ft) R-1 16-25 22 R-2 25-34 31 R-3 >34 42
- 35. API provides4 types of Casing connectors: ◦ CSG short round threads and couplings ◦ LCSG long round threads and couplings ◦ BCSG buttress threads and couplings ◦ XCSG extreme line threads CSG and LCSG combined are called API 8- Round threads
- 36. An intermediatesection of 17.5 size was planned to be drilled at a depth of 14,000 ft. A 13 3/8 OD casing is to be set and cemented in this section. There are four casing types available in stocks which are shown in Table below. Maximum burst pressure has to be assumed when casing is full of 15.8 ppg cement slurry and fluid in the annulus is water. In addition, maximum collapse pressure has to be assumed when casing is full of fresh water and annulus is full of 15.8 ppg cement slurry. Safety factor for burst and collapse was designed to be 1.18 and 1.15 respectively. Design a casing that should be used in this section.
- 37. Depth of thecasing shoe = 14,000 ft Density of cement slurry 15.8 ppg Density of fresh water = 8.34 ppg Collapse safety factor = 1.15 Burst safety factor = 1.18
- 38. Estimate thecollapse and burst pressure for the available casing sizes along with safety factor Then estimate collapse and burst pressure of required depth without safety factor Based on magnitude select the casing
- 39. Estimating Collapsepressure with the help of outer, inner diameter and yield strength Estimating collapse pressure and burst pressure with reference to depth
- 40. For ID12.031 inch
- 42. = 0.052 X14000 X (15.8 – 8.34) = 5430.88 psi = 0.052 X 14000 X (15.8 – 8.34) = 5430.88 psi
- 43. The collapsepressure with safety factor is 5740 and burst pressure is 5961 and the calculated magnitude is 5430.88 which lies between the above values. Thus 12.031 inch ID casing is best.
- 44. Hussain Rabia“Well Engineering and Construction” Hussain Rabia “Oil Well Drilling Engineering Principles and Practice” Hussain and Majid “Fundamental of Sustainable Drilling” “Formulas and Calculations for Drilling Operations” by G.James “Formulas and Calculations for Drilling, Production and Workover” by Lapeyrouse Working Guide to Drilling Equipments and Operations by Williams Lyons Drilling Engineering Workbook by Baker Hughes “Drilling Engineering Technology” by Nediljka Gaurina Medimurec University of Zagreb Advanced Oil Well Drilling Engineering by Mitchell Petroleum Well Construction Directional Drilling by Halliburton Adam.et.al “Applied Drilling Engineering” Drilling Engineering A complete well planning Aprroach by Neal Adam Petroleum Engineering Handbook by Warner Jr. Practical Field Reports I can’t mentioned their names
- 45.