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Presentation 6 casing design

Ali Trichelli
Ali Trichelli

The sixth presentation of a series of presentations on Operations Geology. Very basic, just to introduce beginners to operations geology. I hope the end users will find this and the following presentations very helpful.

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OPERATIONS GEOLOGY PRESENTATIONS Presentation 6: Casing Design 18 November 2016Ali Trichelli
Legend Why Run Casing? Casing Classification Mechanical Properties of Casing Tension Burst Pressure Collapse Pressure Casing Design Criteria Casing Points Selection Other Factors Affecting Casing Points Design Factors API Design Factors
Why Run Casing? To prevent the hole from caving in Onshore - to prevent contamination of fresh water sands To prevent water migration to producing formation To confine production to the wellbore To control pressures during drilling To provide an acceptable environment for subsurface equipment in producing wells To enhance the probability of drilling to total depth (TD)
Casing Classification Casing is classified based on its: Outside diameter (OD) Inside diameter (ID), specified in wall thickness & drift diameter Length (range), specified in 3 major ranges R1 (16-25ft), R2 (25-34ft), R3 (>34ft) Connections, 4 types of connections 5CSG, LCSG, BCSG, XCSG) Weight, expressed in ppf, 3 types of weight (Nominal, Plain-end & average) Grade, expressed as a code and relates to the tensile strength of the steel from which the casing is made
Mechanical Properties of Casing Casing is subjected to different loads during landing, cementing, drilling, and production operations. The most important loads which it must withstand are tensile, burst and collapse loads. Other important loads include wear, corrosion, vibration and pounding by drill pipe, the effects of gun perforating and erosion
Tension Under axial tension, pipe body may suffer 3 possible deformations: Elasticthe metallurgical properties of the steel in the pipe body suffer no permanent damage and it regains its original form if the load is withdrawn Elasto-plasticthe pipe body suffers a permanent deformation which often results in the loss of strength) Plastic
Burst Pressure Minimum expected internal pressure at which permanent pipe deformation could take place, if the pipe is subjected to no external pressure or axial loads.
Collapse Pressure Minimum expected external pressure at which the pipe would collapse if the pipe were subjected to no internal pressure or axial loads.
Casing Design Criteria Casing costs is one of the largest cost items of a drilling project. It is imperative to plan for proper selection of casing strings and their setting depths to realize an optimal and safe well at minimal costs.
Casing Points Selection Initial selection of casing setting depths is based on the pore pressure and fracture pressure gradients for the well. Information on pore pressure and fracture pressure gradients is usually available from offset well data. This information should be contained in the geotechnical information provided for planning the well.
Other Factors Affecting Casing Point Selection Shallow gas zones Lost circulation zones, which limit mud weights Well control Formation stability , which is sensitive to exposure time or mud weight Directional well profile Sidetracking requirements Isolation of fresh water sands (drinking water) Hole cleaning Salt sections High pressured zones Casing shoes should where practicable be set in competent formations Casing program compatibility with existing wellhead systems Casing program compatibility with planned completion program Multiple producing intervals Casing availability Economy
Design Factors Casing design is an optimization process to find the cheapest casing string that is strong enough to withstand the occurring loads over time. API design factors are essentially safety factors that allow us to design safe, reliable casing strings. Each operator may have his own set of design factors, based on his experience and the condition of the pipe. The use of excessively high design factors guarantees against failure but provides excessive strength and, therefore, increased cost. The use of low design factors requires accurate knowledge about the loads to be imposed on the casing as there is less margin available. The company values selected for design factors are a compromise between safety margin and economics.
The API Design Factors The API design factors are: Tension and Joint Strength: DFT= 1.8 Collapse: DFC= 1.125 Burst: DFB= 1.1 Example
Next Presentation Casing & Cementing Overview Casing Accessories & Casing Running Tools Typical Cementing System ( for a land well) The Cementing Job (of a Casing String)

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Presentation 6 casing design

  • 1. OPERATIONS GEOLOGY PRESENTATIONS Presentation 6: Casing Design 18 November 2016Ali Trichelli
  • 2. Legend Why Run Casing? Casing Classification Mechanical Properties of Casing Tension Burst Pressure Collapse Pressure Casing Design Criteria Casing Points Selection Other Factors Affecting Casing Points Design Factors API Design Factors
  • 3. Why Run Casing? To prevent the hole from caving in Onshore - to prevent contamination of fresh water sands To prevent water migration to producing formation To confine production to the wellbore To control pressures during drilling To provide an acceptable environment for subsurface equipment in producing wells To enhance the probability of drilling to total depth (TD)
  • 4. Casing Classification Casing is classified based on its: Outside diameter (OD) Inside diameter (ID), specified in wall thickness & drift diameter Length (range), specified in 3 major ranges R1 (16-25ft), R2 (25-34ft), R3 (>34ft) Connections, 4 types of connections 5CSG, LCSG, BCSG, XCSG) Weight, expressed in ppf, 3 types of weight (Nominal, Plain-end & average) Grade, expressed as a code and relates to the tensile strength of the steel from which the casing is made
  • 5. Mechanical Properties of Casing Casing is subjected to different loads during landing, cementing, drilling, and production operations. The most important loads which it must withstand are tensile, burst and collapse loads. Other important loads include wear, corrosion, vibration and pounding by drill pipe, the effects of gun perforating and erosion
  • 6. Tension Under axial tension, pipe body may suffer 3 possible deformations: Elasticthe metallurgical properties of the steel in the pipe body suffer no permanent damage and it regains its original form if the load is withdrawn Elasto-plasticthe pipe body suffers a permanent deformation which often results in the loss of strength) Plastic
  • 7. Burst Pressure Minimum expected internal pressure at which permanent pipe deformation could take place, if the pipe is subjected to no external pressure or axial loads.
  • 8. Collapse Pressure Minimum expected external pressure at which the pipe would collapse if the pipe were subjected to no internal pressure or axial loads.
  • 9. Casing Design Criteria Casing costs is one of the largest cost items of a drilling project. It is imperative to plan for proper selection of casing strings and their setting depths to realize an optimal and safe well at minimal costs.
  • 10. Casing Points Selection Initial selection of casing setting depths is based on the pore pressure and fracture pressure gradients for the well. Information on pore pressure and fracture pressure gradients is usually available from offset well data. This information should be contained in the geotechnical information provided for planning the well.
  • 11. Other Factors Affecting Casing Point Selection Shallow gas zones Lost circulation zones, which limit mud weights Well control Formation stability , which is sensitive to exposure time or mud weight Directional well profile Sidetracking requirements Isolation of fresh water sands (drinking water) Hole cleaning Salt sections High pressured zones Casing shoes should where practicable be set in competent formations Casing program compatibility with existing wellhead systems Casing program compatibility with planned completion program Multiple producing intervals Casing availability Economy
  • 12. Design Factors Casing design is an optimization process to find the cheapest casing string that is strong enough to withstand the occurring loads over time. API design factors are essentially safety factors that allow us to design safe, reliable casing strings. Each operator may have his own set of design factors, based on his experience and the condition of the pipe. The use of excessively high design factors guarantees against failure but provides excessive strength and, therefore, increased cost. The use of low design factors requires accurate knowledge about the loads to be imposed on the casing as there is less margin available. The company values selected for design factors are a compromise between safety margin and economics.
  • 13. The API Design Factors The API design factors are: Tension and Joint Strength: DFT= 1.8 Collapse: DFC= 1.125 Burst: DFB= 1.1 Example
  • 14. Next Presentation Casing & Cementing Overview Casing Accessories & Casing Running Tools Typical Cementing System ( for a land well) The Cementing Job (of a Casing String)