Tuesday, 17 December 2019

CASING DESIGN - PRODUCTION CASING LOADS DESIGN

PRODUCTION CASING LOAD CASES AND DESIGN

casing burst collapse tension 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


The collapse design load shown in below figure is based on conditions late in the life of the reservoir,
  • 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.


intermediate casing burst collapse design

In the absence of any unusual conditions, the tension design load criteria for production casing are the same as for Surface Casing Design and Intermediate Casing Design. When unusual conditions are present,  maximum  stresses  associated  with  these  conditions  must  be  checked  to determine whether they exceed the design load in any portion of the string.

SEE ALSO

Example Which Shows The Steps And Guidelines Of The Casing Loads Design

Now let's move to the next subject

 THE CASING DESIGN GRAPHICAL METHOD

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