High Collapse

​Collapse loads are seen in all wells. They can be caused by the environment (floating formations such as salt dome), or during drilling / production phases such as cementing operations, full evacuation, and Annular Pressure Build-up (APB).

In some cases, these external pressure cases become critical for the well integrity. The collapse resistance of the casing string can be the limiting factor for the design selection.

​Challenges

Pre-salt areas

 

High shear loads on the casing string.

Non-uniform collapse pressure difficult to evaluate accurately.

High safety margin should be taken regarding collapse resistance.

Annular pressure build-up

In HP/HT offshore wells, in absence of pressure release possibility, the increase of annulus fluid temperature induces uniform external pressure on the casing. One main concern will be on the intermediate casing (usually 13 3/8"), that is intrinsically weak in collapse. Thicker pipes (13 5/8", 14", in High Collapse grades) are usually advised to overcome the APB issues.

Other collapse issues

During drilling and production phases, different cases of external pressure occur. A main example is the full evacuation scenario, where the hydrostatic pressure of the external annulus will apply collapse load on the casing, especially on the non-cemented parts.

​​Solutions

Vallourec has developed and designed specific solutions to overcome collapse challenges:

  • High Collapse grades, with significant increase of the collapse resistance compared to standard API 5CT pipe, by optimizing mechanical and dimensional
  • Thick flush and semi-flush connection design (such as VAM® MUST), providing thicker walls than the Threaded and Coupled product, but with same clearance and drift
  • Odd sizes (9 7/8", 10", 13 5/8", 14"…) to provide thicker pipes while keeping the drift, preferably with special clearance or Integral connections
  • Mixed strings with thick wall sections in the case of severe salt area to pass through.​
 
Vallourec​ is a world leader in providing solutions for high collapse challenges, which is supported through a strong engineering, Research and development teams, testing facilities and manufacturing capabilities.