¶ Tubing Evacuation
Tubing evacuation load is a collapse load on the production tubing. Internal pressure is constructed as -
- fraction of tubing to which the tubing is evacuated. Default fraction is 0.5
- fluid density inside the tubing below the evacuation. Default density is 2.5 ppg
Top of fluid column is calculated as - sdrop = x × sEOT Then convert the measured depth sdrop to true vertical depth zdrop zdrop = [sdrop] → convert to TVD where,
- sEOT = measured depth of the end of tubing, ft MD
- sdrop = measured depth of the fluid column drop, ft MD
- zdrop = true vertical depth of the fluid column drop, ft TVD
- x = fraction of tubing
¶ Internal pressure profile
The internal pressure profile will be calculated using the following equation -
- Pi(z) = C * pi * (z - zdrop) for z > zdrop
- Pi(z) = 0 for z ≤ drop
where,
- z = true vertical depth of interest, ft TVD
- pi(z) = internal pressure at z, psi
- ρi = internal fluid density, ppg
¶ External pressure profile
External pressure assumes trapped original packer fluid above the packer and same as internal pressure below the packer.
- pe(z) = C * ppacker * z for z ≤ zpacker
- pe(z) = C * pi * (z - zdrop) for z > zpacker and z > zdrop
- 0 for z > zpacker and z ≤ zdrop
where,
- pe(z) = external pressure at z, psi
- ρpacker = packer fluid density, ppg
- zpacker = true vertical depth of packer, ft TVD
¶ Temperature profile
Undisturbed temperature is assumed as the temperature profile for this load case.
¶ Data inputs
An example of internal and external pressure profiles for tubing evacuation load case. Input form of this load case:
- Description - Enter an appropriate name for the load to replace the default name.
- Pressure at Hanger outside the tubing - Default value is shown based on the calculation described earlier. User can change this pressure as appropriate.
- Fluid Density Inside Tubing - Enter an appropriate tubing fluid density. Default density is 2.5 ppg.
- Fraction of Tubing Evacuated (0 - 1.0) - Enter an appropriate fraction to replace the default tubing fraction of fluid evacuation.
- Fluid Drop Depth - It is calculated based on the fraction of tubing evacuated. It is not an input.
- Temperature Profile - Select an appropriate temperature profile for this load case. Undisturbed temperature has been selected as default.
- Packer Setting - Select appropriate external fluid to the packer depth. Default packer fluid density is picked from the casing program.
- Section Bottom - Fluid below the packer is being selected as the tubing fluid. The density is entered earlier.
