PRODUCTION CASING LOAD CASES AND DESIGN
The Casing Burst Design Loads Assumption
- A producing well has an initial shut-in BHP equal to the formation pore pressure.
- A gaseous produced fluid in the well.
- The Production Casing must be designed so that it will not fail if the tubing fails.
- A tubing leak is assumed to be possible at any depth.
- It generally is also assumed that the density of the completion fluid in the casing above the packer is equal to the density of the mud left outside the casing.
- If a tubing leak occurs near the surface, the effect of the hydrostatic pressure of the completion fluid in the casing would negate the effect of the external mud pressure on the casing.
- Mud degradation outside the casing is neglected because the formation pore pressure of any exposed formation would nearly equal the mud hydrostatic pressure.
The Casing Collapse Design Loads Assumption
- When reservoir pressure has been depleted to a very low (negligible) abandonment pressure.
- A leak in the tubing or packer could cause the loss of the completion fluid, so the low internal pressure is not restricted to just the portion of the casing below the packer.
- Thus, for design purposes, the entire casing is considered empty.
- The fluid density outside the casing is assumed to be that of the mud in the well when the casing was run.
- The beneficial effect of the cement is ignored.